Pop-up enclosures are known having a body portion that is recessed into a table top and a top plate that is substantially flush with the table and lifts off to provide access to connectors that are concealed when the top plate is closed. Such pop-up enclosures are described, for example, in U.S. Pat. No. 6,802,577, which describes an enclosure system having a saddle that is attached to a bezel and defines an open area for receiving an enclosure. The bezel defines an opening for receiving a top plate of the enclosure. An outer perimeter of the bottom surface of the bezel rests on edges of an opening cut through a table top. The enclosure pivots from a concealed position, in which the top plate is flush with the bezel, to an open position in which the face plate of the enclosure is exposed. A spring biases the enclosure towards the open position, while a latch maintains the enclosure in the concealed position.
As shown in FIG. 1 of U.S. Pat. No. 6,802,577, the top plate swings about a hinge axis close to a rear edge of the top plate. In the device disclosed by U.S. Pat. No. 6,802,577, the spring bias is constituted by a gas spring comprising a body into which a piston may be extended and retracted. In the normal state, the gas spring is extended and exerts force on the piston, which is thus applied to a lower inside surface of the top plate so as to urge it open. The top plate is closed against the force of the retracted gas spring and is latched by a catch so as to restrain the top plate in the closed position where it is flush with the top surface of the enclosure system. A similar arrangement is shown in U.S. Pat. No. 3,992,070.
Since the force exerted by the gas spring is predetermined by the type of device used and is generally a function of size, some tradeoff is usually called for between the desire for compactness of the pop-up enclosure, on the one hand, and the requirement that the top plate operate effectively, on the other. These two desiderata are, to some extent, mutually exclusive as will now be explained with reference to FIGS. 1 to 3 showing schematically in cross-section a detail of a prior art pop-up enclosure 10. The enclosure 10 includes a top plate 11 that has a rear edge 12 and is hingedly attached by a hinge axis 13 to a receptacle 14 that is flush mounted with a work surface 15. A gas spring 16 is pivotally anchored at one end 17 to an inside of the receptacle 14, its opposite end being pivotally attached to a support 18 mounted on the inner surface of the top plate 11 so as to be rotatable about a pivot axis 19.
Electronic equipment such as video, audio and power sockets represented by the box 20 in FIGS. 2 and 3 are mounted inside the receptacle 14 so as to be concealed by the top plate 11 when closed while being accessible when open. The equipment 20 occupies most of the central region of the receptacle, which limits the point on the lower surface of the top plate to where the gas spring 16 may be fixed. Specifically, the location of the pivot axis 19 determines the point of application of force by the gas spring 16, such that the greater the distance between the hinge axis 13 the pivot axis 19, the greater is the applied moment (for a given gas spring force) and vice versa. However, since most of the space within the receptacle is occupied, the gas spring 16 needs to be mounted behind the equipment. This generally requires that it be anchored via a bracket 21 that is fixed to an inner surface of the receptacle or an outer surface of the equipment 20. As the top plate opens, the gas spring extends and turns about its point of attachment to the bracket 21. Regardless of whether the bracket 21 is anchored to the receptacle or the equipment, it is clear that as the support 18 moves further away from the hinge axis 13, the lower point of attachment of the gas spring 16 must move further away from the equipment 20. This is well demonstrated in FIG. 3, which compares the two arrangements in FIGS. 1 and 2, the arrangement in FIG. 2 being illustrated by the dashed line.
It thus emerges that while mounting the support 18 farther away from the hinge axis 13 increases the moment of the gas spring 16 and facilitates opening of the top plate, it militates against compactness of the pop-up assembly.
Consequently, compactness is increased by bringing the pivot axis 19 closer to the hinge axis 13.
US D553,306 in the name of FSR, Inc. discloses a tabletop mounted connection box having a circular lid that turns about a hinge axis located toward a rear of the lid. Owing to its circular profile, the device is easily installed by drilling a hole in a work surface using a drill-mounted hole-saw, which is well within the capability of the average homeowner. The device is sold under the catalog names T3-AC2/T3-PC1/T3-PC1D and offers a low footprint and easy installation. However, it is designed for manual operation by pressing down on a tip of the lid near the hinge as shown to schematically in FIG. 4. This requires that the hinge axis 13 be displaced from the ridge of the lid in order to be able to apply an adequate moment.
It would be an advantage to use a gas spring or similar resilient bias force to lift the lid automatically. Theoretically, this might be done by anchoring a spring to a support pivot mounted near the ridge underneath the lid so as to apply a tensile force that turns the lid about the hinge axis. In practice, it does not appear to be feasible to do this to the device shown in US D553,306 for a number of reasons. First, the lid is connected to a concealed hinge via a bracket that is fixed to the lower surface of the lid with the result that the lid is vertical when fully opened. A spring would need to be affixed to the edge of the lid to pull it open to a vertical orientation and this is both neither esthetic nor practical. On the other hand, a spring mounted on the lower surface of the lid near the ridge will result in the lid being incompletely opened, thus restricting access to the equipment therein.
A gas spring is preferable to a coil spring because it opens slowly and in a controlled manner unlike a coil spring, which opens almost instantaneously upon release, resulting in too aggressive an action. However, the difficulties are compounded when attempting to automate opening of the lid using a gas spring without derogating from the compactness of the unit, as explained above.